package org.fisco.bcos.web3j.crypto.gm.sm2.crypto;

/**
 * A wrapper class that allows block ciphers to be used to process data in a piecemeal fashion. The
 * BufferedBlockCipher outputs a block only when the buffer is full and more data is being added, or
 * on a doFinal.
 *
 * <p>Note: in the case where the underlying cipher is either a CFB cipher or an OFB one the last
 * block may not be a multiple of the block size.
 */
public class BufferedBlockCipher {
    protected byte[] buf;
    protected int bufOff;

    protected boolean forEncryption;
    protected BlockCipher cipher;

    protected boolean partialBlockOkay;
    protected boolean pgpCFB;

    /** constructor for subclasses */
    protected BufferedBlockCipher() {}

    /**
     * Create a buffered block cipher without padding.
     *
     * @param cipher the underlying block cipher this buffering object wraps.
     */
    public BufferedBlockCipher(BlockCipher cipher) {
        this.cipher = cipher;

        buf = new byte[cipher.getBlockSize()];
        bufOff = 0;

        //
        // check if we can handle partial blocks on doFinal.
        //
        String name = cipher.getAlgorithmName();
        int idx = name.indexOf('/') + 1;

        pgpCFB = (idx > 0 && name.startsWith("PGP", idx));

        if (pgpCFB || cipher instanceof StreamCipher) {
            partialBlockOkay = true;
        } else {
            partialBlockOkay = (idx > 0 && (name.startsWith("OpenPGP", idx)));
        }
    }

    /**
     * return the cipher this object wraps.
     *
     * @return the cipher this object wraps.
     */
    public BlockCipher getUnderlyingCipher() {
        return cipher;
    }

    /**
     * initialise the cipher.
     *
     * @param forEncryption if true the cipher is initialised for encryption, if false for
     *     decryption.
     * @param params the key and other data required by the cipher.
     * @exception IllegalArgumentException if the params argument is inappropriate.
     */
    public void init(boolean forEncryption, CipherParameters params)
            throws IllegalArgumentException {
        this.forEncryption = forEncryption;

        reset();

        cipher.init(forEncryption, params);
    }

    /**
     * return the blocksize for the underlying cipher.
     *
     * @return the blocksize for the underlying cipher.
     */
    public int getBlockSize() {
        return cipher.getBlockSize();
    }

    /**
     * return the size of the output buffer required for an update an input of len bytes.
     *
     * @param len the length of the input.
     * @return the space required to accommodate a call to update with len bytes of input.
     */
    public int getUpdateOutputSize(int len) {
        int total = len + bufOff;
        int leftOver;

        if (pgpCFB) {
            leftOver = total % buf.length - (cipher.getBlockSize() + 2);
        } else {
            leftOver = total % buf.length;
        }

        return total - leftOver;
    }

    /**
     * return the size of the output buffer required for an update plus a doFinal with an input of
     * 'length' bytes.
     *
     * @param length the length of the input.
     * @return the space required to accommodate a call to update and doFinal with 'length' bytes of
     *     input.
     */
    public int getOutputSize(int length) {
        // Note: Can assume partialBlockOkay is true for purposes of this calculation
        return length + bufOff;
    }

    /**
     * process a single byte, producing an output block if necessary.
     *
     * @param in the input byte.
     * @param out the space for any output that might be produced.
     * @param outOff the offset from which the output will be copied.
     * @return the number of output bytes copied to out.
     * @exception DataLengthException if there isn't enough space in out.
     * @exception IllegalStateException if the cipher isn't initialised.
     */
    public int processByte(byte in, byte[] out, int outOff)
            throws DataLengthException, IllegalStateException {
        int resultLen = 0;

        buf[bufOff++] = in;

        if (bufOff == buf.length) {
            resultLen = cipher.processBlock(buf, 0, out, outOff);
            bufOff = 0;
        }

        return resultLen;
    }

    /**
     * process an array of bytes, producing output if necessary.
     *
     * @param in the input byte array.
     * @param inOff the offset at which the input data starts.
     * @param len the number of bytes to be copied out of the input array.
     * @param out the space for any output that might be produced.
     * @param outOff the offset from which the output will be copied.
     * @return the number of output bytes copied to out.
     * @exception DataLengthException if there isn't enough space in out.
     * @exception IllegalStateException if the cipher isn't initialised.
     */
    public int processBytes(byte[] in, int inOff, int len, byte[] out, int outOff)
            throws DataLengthException, IllegalStateException {
        if (len < 0) {
            throw new IllegalArgumentException("Can't have a negative input length!");
        }

        int blockSize = getBlockSize();
        int length = getUpdateOutputSize(len);

        if (length > 0) {
            if ((outOff + length) > out.length) {
                throw new OutputLengthException("output buffer too short");
            }
        }

        int resultLen = 0;
        int gapLen = buf.length - bufOff;

        if (len > gapLen) {
            System.arraycopy(in, inOff, buf, bufOff, gapLen);

            resultLen += cipher.processBlock(buf, 0, out, outOff);

            bufOff = 0;
            len -= gapLen;
            inOff += gapLen;

            while (len > buf.length) {
                resultLen += cipher.processBlock(in, inOff, out, outOff + resultLen);

                len -= blockSize;
                inOff += blockSize;
            }
        }

        System.arraycopy(in, inOff, buf, bufOff, len);

        bufOff += len;

        if (bufOff == buf.length) {
            resultLen += cipher.processBlock(buf, 0, out, outOff + resultLen);
            bufOff = 0;
        }

        return resultLen;
    }

    /**
     * Process the last block in the buffer.
     *
     * @param out the array the block currently being held is copied into.
     * @param outOff the offset at which the copying starts.
     * @return the number of output bytes copied to out.
     * @exception DataLengthException if there is insufficient space in out for the output, or the
     *     input is not block size aligned and should be.
     * @exception IllegalStateException if the underlying cipher is not initialised.
     * @exception InvalidCipherTextException if padding is expected and not found.
     * @exception DataLengthException if the input is not block size aligned.
     */
    public int doFinal(byte[] out, int outOff)
            throws DataLengthException, IllegalStateException, InvalidCipherTextException {
        try {
            int resultLen = 0;

            if (outOff + bufOff > out.length) {
                throw new OutputLengthException("output buffer too short for doFinal()");
            }

            if (bufOff != 0) {
                if (!partialBlockOkay) {
                    throw new DataLengthException("data not block size aligned");
                }

                cipher.processBlock(buf, 0, buf, 0);
                resultLen = bufOff;
                bufOff = 0;
                System.arraycopy(buf, 0, out, outOff, resultLen);
            }

            return resultLen;
        } finally {
            reset();
        }
    }

    /**
     * Reset the buffer and cipher. After resetting the object is in the same state as it was after
     * the last init (if there was one).
     */
    public void reset() {
        //
        // clean the buffer.
        //
        for (int i = 0; i < buf.length; i++) {
            buf[i] = 0;
        }

        bufOff = 0;

        //
        // reset the underlying cipher.
        //
        cipher.reset();
    }
}
